Metcury pendulum contact



y 16, 1933- B. TOWNSHEND 1,909,555

MERCURY PENDULUMv CONTACT Filed July 6, 1927 53w Zz's my? Patented May 16, 1933 UETED STATES PATENT oFFiE BAILEY TOWNSHEND, OF JACKSON HEIGHTS, NEW YORK, ASSIGNOR TO INTERNA- TIONAL TIME RECORDING COMPANY OF NEW YORK, OF ENDIOOTT, NEVT YORK, .A

CORPORATION OF NEW YORK MERCURY PENDULUM CONTACT Application filed July 6,

This invention refers to a contacting mechanism for providing for the emission of impulses closely timed as to Occurrence and duration and governed by a master clock. The mechanism is also of such a nature as to permit a series of such impulses which may be of frequence substantially .as high as desired. 1'

The most feasible methods of obtaining such a series of impulses is from the pendulum of the master clock and both spring and mercury contacts have been devised for this purpose. Spring contacts, however, form such a drag on the pendulum as to greatly impair the accuracy of its swing. Furthermore, such spring contacts invariably introduce inaccuracies in the duration and time of occurrence of the impulses. Mercury contacts heretofore used have consisted of a trough or cup of mercury through which an electrical contact on the end of the clock pendulum swings, the contact being made with the mercury when the pendulum is swinging with its maximum force so that the tendency to retard the pendulum is less afiected. swing as above stated, the mercury trough has to be sufiiciently long to permit the pendulum contact as it swings through its arc to pass over the rim of the trough of mercury, drop down into the mercury, rise out of the mercury and pass over the opposite rim of the trough. The electrical contact on the end of the pendulum is in engagement with the mercury for an appreciable time, whereupon the duration of the impulses has been limited to a predetermined minimum and furthermore, the dura- 1 tion of all impulses has not been uniform.

It is contemplated, according to the present invention, to cause an electrical contact on the end of a clock pendulum to make contact with a trough or narrow slot filled with mercury so that the contact swings through the meniscus projecting above the trough. The trough or slot is placed crosswise to the path of swing of the pendulum. The impulses may be made short and accurate in this manner and owing to the elongated form of the mercury con- In order for the pendulum to 1927. Serial No. 203,721.

tact extreme accuracy of adjustment of the plane of swing of the pendulum is unnecessary. With a trough or slot so constructed, however, it has been found that the quick passage of the pendulum contact through '7 the mercury has a tendency to drag some of it out of the trough. Provision has been made for a type of mercury trough or slot wherein it will be impossible for the pendulum contact to remove the meniscus. I have found that by providing a mercury trough in the form of a block having an undercut slot therein, which slot is wider at the bottom than at the top the tendency for the pendulum contact to drag any of the mercury out of its slot is eliminated. Under these conditions the mercury forms a me niscus arching above the walls of the trough thereby obtaining a good means for securing a line of mercury for the contacting surface. Mercury, as is well known, has a tendency, owing to its surface tension, to assume a spherical shape or at least form a globule. In thepresent case, owing to the undercut configuration of the retaining slot, this tendency manifests itself as a pressure against the inclined walls which results in spreading out of the globule causing it to substantially fill the slot and present a meniscus which projects above the block to a lesser degree than would be the case' if the slot were provided with vertical walls. In other words, the undercut slot walls exert a downward pressure on the mercury which wedges, holds down, or looks the mercury therein. It was found that with such a construction that it was possible to tip the trough or slot at an angle of thirty degrees without the contents becoming dislodged.

There is a tendency for the exposed surface of mercury to become oxidized and likewise to collect dust forming an insulating scum on it. If a wire or needle point contact is used, this scum has a tendency to collect on it and eventually insulate it. This has been avoided by using an elongated electrical contact with sharp edges so arranged as to cut through the scum formed on the mercury instead of gathering it on the contact point. Preferably this contact is made of platinum-iridium which was found to be particularly suitable as it is less susceptible to pitting due to arcing and also provides for good electrical contact owing to the tendency of mercury to wet the platinum.

In the accompanying drawing I have shown for purpose of illustration one form of mechanism embodying the invention in which: i

Fig. 1 is a front elevation of a pendulum for a master clock with the mercury contacting device associated therewith.

Fig. 2 is a plan view of the mercury contacting device taken on line 22 of Fig. 1.

Fig. 3 is a sectional View taken on line 38 of Fig. 2.

Fig. 4 is a sectional View taken on line 4.4l of Fig. 8 on a slightly smaller scale.

Fig. 5 is a detail of the contact blade carried by the pendulum.

Fig. 6 is a section taken on line 66 of Fig. 5 showing the shape of the blade.

Reference will now be had to the drawing wherein what is now believed to be the preferred form of mercury contacting device is illustrated. Referring to Fig. 1, the invention is shown as applied to a master clock of the mercurial pendulum type, the pendulum, verge and frame being shown at 10, 11 and 12, respectively. Mounted on the pendulum 10 are the usual mercury jars 13 and an adjusting nut 14 for regulating the oscillation of the pendulum. Aiiixed to the end of the pendulum is a diamond or wedge-shaped knife contact 15 (Figs. 5 and 6) which cuts through any scum which may form on the mercury without dragging the particles of mercury out of the slot. The front and rear edges 40 and l1 respectively are sharpened so that as the leading edge of the blade reaches the mercury it cuts through the scum and as the trailing et ge passes, the mercury will quickly fill the space being vacated by the blade, thus avoiding he tendency to create the vacuum which would otherwise retard or act as a drag upon the pendulum. The lower edge 42 of the blade is also sharp so as to give a downward cutting action through the scum to insure a clean contacting surface for the mercury. This construction may be seen in Figs. 5 and 6 in which Fig. 5 shows an enlarged sectional view of knife contact and Fig. fishows a sectional view taken near the lower end of the blade showing the sharp leading and rear edge thereof.

The mercury contact device is illustrated in detail in Figs. 2, 3 and 4:. The device comprises a block 154 having an undercut slot 16 therein, the front and rear walls 17 and 18 being slightly undercut to form dovetail grooves as viewed in Fig. Slidably mounted for longitudinal movement in these grooves is a mercury trough 19. This trough has an undercut slot 20 therein which slot is cut so that the bottom 21, Fig. 3, is

wider than the top 22. Upon depositing mercury in the slot 20, it will engage the sides and bottom of the trough and spread so as to fill it as shown in 23 and 4. The mercury will form a meniscus arching above the sides of the trough so that the pendulum may swing through the mercury without touching the sides of the trough. Vfith such a construction, either the accidental spilling of the mercury or any part oi the meniscus being knocked off by the passage of the pendulum, is eliminated. Adjusting screws 23 are mounted on the sides of the block 1560 so that the mercury trough 19 may be easily adjusted longitudinally with respect to the contact on the end of the clock pendulum and thereby insure contact at the mid-point of pendulum swing. Lock nuts 2% are provid d on the set screws so that the set screws may be locked into position after the mercury trough has been adjusted. The block 15a is tapped to receive circular stud 25 having an opening therein at 26. This circular stud fits into a corresponding hole 27 in a block 28, relative rotary movement between the lock and the stud being prevented by a lug 29 on the stud 25 sliding in a groove in block 28. The block 28 is rigid with a bracket 30 which bracket is mounted on the clock case as viewed in Figs. 2 and 1. An adjusting screw 31 coacts with screw threads in the block 28 and has a smooth reduced end engaging the opening in the stud 25. This screw is adapted to move the stud 25 and the block 15a against the tension of the springs 33 mounted at one end to the pins 3 1 on the bracket 30 and at their other ends on the lugs 35 on the block 1545. A lock nut 36 is provided to keep the set screw 31 in the position. to which it has been adjusted. A set screw 87 is provided in the block 150: to bear against the mercury trough 19 thereby locking it firi'nly in any set position. An electric circuit to be controlled by the contacting mechanism may be connected to the frame 12 supporting the pendulum and to the bracket 30 supporting the mercury contact as indicated at 39 and 38, respectively.

The particular embodiment of the mercury trough or slot shown is adapted to the usual commercial metals which are not wet by mercury. If a metal is used wh ch is wet by mercury, for example platinum, it may be unnecessary to undercut the slot containing the mercury, as with such metals there is a tendency for the mercur to stick to the sides of the slot. Gn account of the expense of these metals, it is preferred to use the commoner metals with the undercut slot as shown.

While I have shown and described and pointed out the fundamental novel features of the invention as applied to a single modification it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art Without departing from the spirit of the invention. I intend to be limited therefore only as indicated by the scope of the following claims.

I claim:

1. A time controlled circuit closer comprising an elongated mercury contact, a coacting contact element mounted on a period ically operating member to contact at predetermined intervals with the mercury contact and swingable past opposite sides of the mercury contact, said mercury contact being located with its longer dimension extending substantially normal to the path of movement of the moving contact and means for adjusting the mercury contact in the direction of travel of the moving contact to permit accurate timing of the engagement of the two contacts.

2. A circuit closer comprising a mercury contact consisting of a conducting member having a slot with undercut side walls and a mercury column in said slot, the undercut Walls of said slot exerting a downward pressure on the mercury column to hold down the mercury and result in the mercury col umn forming a meniscus projecting slightly above the slot to a lesser degree than normal for the amount of mercury in the slot.

3. A circuit closer comprising a mercury contact consisting of a conducting member having a slot with undercut side walls and sufficient mercury in said slot to form a meniscus projecting slightly above the top of the undercut walls of said slot to a lesser degree than normal for the exposed dimensions of the slot, the undercut walls of the slot serving to press downwardly on the mercury in the slot to hold down the mercury therein.

4:. A circuit closer comprising a mercury contact consisting of a contact member having a slot with a closed bottom and inclined side walls extending from the closed bottom and converging towards the top of the slot, there being suflicient mercury in said slot to form a meniscus projecting slightly above the top of the undercut walls of said slot to a lesser degree than normal for the exposed dimensions of the slot, the inclined side walls of the slot pressing downwardly on the mercury in the slot to hold down the mercury therein.

5. A circuit closer comprising a mercury contact and a relatively movable contact coacting therewith, said movable contact pro vided with facets at the end which are symmetrically deposed relative to the central plane of travel of the movable contact, the facets being at similar angles to said central plane and intersecting each other at an acute angle to provide at the intersection a sharp edge lying in said central plane and extending longitudinally of the movable contact to cut through the mercury.

6. A circuit closer comprising a mercury contact and a relatively movable contact coacting therewith, said movable contact provided with a pyramidal tip the facets of which are substantially symmetrically disposed relative to the central plane of travel of the movable contact to form a pair of sharp cutting edges lying within said central plane of travel, these edges being at opposite sides of the movable contact, one edge cutting through the mercury when the movable contact is moving in one direction, and the other edge cutting through the mercury when the movable contact is moving in the opposite direction.

7. In a circuit closer including a period ically moving member, a contact device for cooperating with said member, said device comprising a mercury container past both sides of which said member is movable, a carrier having guideways for slidably guiding said container on said carrier and screws provided on said carrier on each side of said container for adjusting the container on said carrier and holding the container in adjusted position.

8. In a circuit closer including a periodically moving member, a contact mechanism for cooperating with said member, said mechanism comprising a contact device, a carrier on which said device is vertically movable, spring means for restraining such vertical movement, and an adjusting member for moving the device vertically against said spring means and holding it stationarily in adjusted position.

In testimony whereof I hereto affix my signature.

' BAILEY TOWN SHEND. 

